[U-Boot] [patch] rm9200 lowevel_init: don't touch reserved/readonly registers
For some reason the AT91rm9200 lowlevel init writes to a bunch of reserved or read-only addresses. All the boards seem to define the value-to-be-written values as zero ... but they shouldn't actually be writing *anything* there.
No documented erratum justifies these accesses. It looks like maybe some pre-release BDI-2000 setup code has been carried along by cargo cult programming since at least late 2004 (per GIT history).
Here's a patch disabling what seems to be bogosity. Tested on a csb337; there were no behavioral changes. --- cpu/arm920t/at91rm9200/lowlevel_init.S | 14 ++------------ include/configs/at91rm9200dk.h | 5 ----- include/configs/at91rm9200ek.h | 5 ----- include/configs/cmc_pu2.h | 5 ----- include/configs/csb637.h | 5 ----- include/configs/m501sk.h | 5 ----- include/configs/mp2usb.h | 5 ----- 7 files changed, 2 insertions(+), 42 deletions(-)
--- a/cpu/arm920t/at91rm9200/lowlevel_init.S +++ b/cpu/arm920t/at91rm9200/lowlevel_init.S @@ -81,6 +81,7 @@ LoopOsc: bne 0b /* delay - this is all done by guess */ ldr r0, =0x00010000 + /* (vs reading PMC_SR for LOCKA, LOCKB ... or MOSCS earlier) */ 1: subs r0, r0, #1 bhi 1b @@ -108,16 +109,6 @@ LoopOsc: .ltorg
SMRDATA: - .word AT91C_MC_PUIA - .word CONFIG_SYS_MC_PUIA_VAL - .word AT91C_MC_PUP - .word CONFIG_SYS_MC_PUP_VAL - .word AT91C_MC_PUER - .word CONFIG_SYS_MC_PUER_VAL - .word AT91C_MC_ASR - .word CONFIG_SYS_MC_ASR_VAL - .word AT91C_MC_AASR - .word CONFIG_SYS_MC_AASR_VAL .word AT91C_EBI_CFGR .word CONFIG_SYS_EBI_CFGR_VAL .word AT91C_SMC_CSR0 @@ -128,8 +119,7 @@ SMRDATA: .word CONFIG_SYS_PLLBR_VAL .word AT91C_MCKR .word CONFIG_SYS_MCKR_VAL - /* SMRDATA is 80 bytes long */ - /* here there's a delay of 100 */ + /* here there's a delay */ SMRDATA1: .word AT91C_PIOC_ASR .word CONFIG_SYS_PIOC_ASR_VAL --- a/include/configs/at91rm9200dk.h +++ b/include/configs/at91rm9200dk.h @@ -45,11 +45,6 @@ #ifndef CONFIG_SKIP_LOWLEVEL_INIT #define CONFIG_SYS_USE_MAIN_OSCILLATOR 1 /* flash */ -#define CONFIG_SYS_MC_PUIA_VAL 0x00000000 -#define CONFIG_SYS_MC_PUP_VAL 0x00000000 -#define CONFIG_SYS_MC_PUER_VAL 0x00000000 -#define CONFIG_SYS_MC_ASR_VAL 0x00000000 -#define CONFIG_SYS_MC_AASR_VAL 0x00000000 #define CONFIG_SYS_EBI_CFGR_VAL 0x00000000 #define CONFIG_SYS_SMC_CSR0_VAL 0x00003284 /* 16bit, 2 TDF, 4 WS */
--- a/include/configs/at91rm9200ek.h +++ b/include/configs/at91rm9200ek.h @@ -56,11 +56,6 @@ #ifndef CONFIG_SKIP_LOWLEVEL_INIT #define CONFIG_SYS_USE_MAIN_OSCILLATOR 1 /* flash */ -#define CONFIG_SYS_MC_PUIA_VAL 0x00000000 -#define CONFIG_SYS_MC_PUP_VAL 0x00000000 -#define CONFIG_SYS_MC_PUER_VAL 0x00000000 -#define CONFIG_SYS_MC_ASR_VAL 0x00000000 -#define CONFIG_SYS_MC_AASR_VAL 0x00000000 #define CONFIG_SYS_EBI_CFGR_VAL 0x00000000 #define CONFIG_SYS_SMC_CSR0_VAL 0x00003284 /* 16bit, 2 TDF, 4 WS */
--- a/include/configs/cmc_pu2.h +++ b/include/configs/cmc_pu2.h @@ -44,11 +44,6 @@ #ifndef CONFIG_SKIP_LOWLEVEL_INIT #define CONFIG_SYS_USE_MAIN_OSCILLATOR 1 /* flash */ -#define CONFIG_SYS_MC_PUIA_VAL 0x00000000 -#define CONFIG_SYS_MC_PUP_VAL 0x00000000 -#define CONFIG_SYS_MC_PUER_VAL 0x00000000 -#define CONFIG_SYS_MC_ASR_VAL 0x00000000 -#define CONFIG_SYS_MC_AASR_VAL 0x00000000 #define CONFIG_SYS_EBI_CFGR_VAL 0x00000000 #define CONFIG_SYS_SMC_CSR0_VAL 0x100032ad /* 16bit, 2 TDF, 4 WS */
--- a/include/configs/csb637.h +++ b/include/configs/csb637.h @@ -45,11 +45,6 @@ #ifndef CONFIG_SKIP_LOWLEVEL_INIT #define CONFIG_SYS_USE_MAIN_OSCILLATOR 1 /* flash */ -#define CONFIG_SYS_MC_PUIA_VAL 0x00000000 -#define CONFIG_SYS_MC_PUP_VAL 0x00000000 -#define CONFIG_SYS_MC_PUER_VAL 0x00000000 -#define CONFIG_SYS_MC_ASR_VAL 0x00000000 -#define CONFIG_SYS_MC_AASR_VAL 0x00000000 #define CONFIG_SYS_EBI_CFGR_VAL 0x00000000 #define CONFIG_SYS_SMC_CSR0_VAL 0x00003284 /* 16bit, 2 TDF, 4 WS */
--- a/include/configs/m501sk.h +++ b/include/configs/m501sk.h @@ -46,11 +46,6 @@ */ #define CONFIG_SYS_USE_MAIN_OSCILLATOR 1 /* flash */ -#define CONFIG_SYS_MC_PUIA_VAL 0x00000000 -#define CONFIG_SYS_MC_PUP_VAL 0x00000000 -#define CONFIG_SYS_MC_PUER_VAL 0x00000000 -#define CONFIG_SYS_MC_ASR_VAL 0x00000000 -#define CONFIG_SYS_MC_AASR_VAL 0x00000000 #define CONFIG_SYS_EBI_CFGR_VAL 0x00000000 #define CONFIG_SYS_SMC_CSR0_VAL 0x00003284 /* 16bit, 2 TDF, 4 WS */
--- a/include/configs/mp2usb.h +++ b/include/configs/mp2usb.h @@ -49,11 +49,6 @@ #ifndef CONFIG_SKIP_LOWLEVEL_INIT #define CONFIG_SYS_USE_MAIN_OSCILLATOR 1 /* flash */ -#define CONFIG_SYS_MC_PUIA_VAL 0x00000000 -#define CONFIG_SYS_MC_PUP_VAL 0x00000000 -#define CONFIG_SYS_MC_PUER_VAL 0x00000000 -#define CONFIG_SYS_MC_ASR_VAL 0x00000000 -#define CONFIG_SYS_MC_AASR_VAL 0x00000000 #define CONFIG_SYS_EBI_CFGR_VAL 0x00000000 #define CONFIG_SYS_SMC_CSR0_VAL 0x00003084 /* 16bit, 2 TDF, 4 WS */
On 18:40 Thu 16 Jul , David Brownell wrote:
For some reason the AT91rm9200 lowlevel init writes to a bunch of reserved or read-only addresses. All the boards seem to define the value-to-be-written values as zero ... but they shouldn't actually be writing *anything* there.
No documented erratum justifies these accesses. It looks like maybe some pre-release BDI-2000 setup code has been carried along by cargo cult programming since at least late 2004 (per GIT history).
Here's a patch disabling what seems to be bogosity. Tested on a csb337; there were no behavioral changes.
cpu/arm920t/at91rm9200/lowlevel_init.S | 14 ++------------ include/configs/at91rm9200dk.h | 5 ----- include/configs/at91rm9200ek.h | 5 ----- include/configs/cmc_pu2.h | 5 ----- include/configs/csb637.h | 5 ----- include/configs/m501sk.h | 5 ----- include/configs/mp2usb.h | 5 ----- 7 files changed, 2 insertions(+), 42 deletions(-)
Tested on rm9200ek
applied to u-boot-arm
Best Regards, J.
participants (2)
-
David Brownell -
Jean-Christophe PLAGNIOL-VILLARD